In the handling of sheets, particularly documents such as business forms, as a sheet is being conveyed in a particular direction, often the leading edge thereof will become skewed--that is, the leading edge is not perpendicular to the direction of conveyance, but assumes a particular angular orientation (a skew angle). If the sheet is skewed when presented to a device for rotating it through a finite angle, such as described in the parent application, then the sheet will not be rotated to a second orientation which is the desired orientation, but will differ by the skewed angle (either being greater or lesser than desired) by the amount of the skew angle. If the document--with the leading edge not positioned as desired--is then fed into a pressure sealer, such as the Moore commercial "Speedisealer.RTM." pressure seal system, the pressure rolls may pass over only a portion of the edge, thus sealing only a half or a third of the edge of the document, which could result in reject of the form, or the form could be damaged when mailed or otherwise handled. In this, and in many other situations, it is thus important to have the form positioned so that the leading edge thereof is perpendicular to the direction of conveyance into a piece of equipment.
According to the present invention, a method and apparatus are provided for simply and effectively correcting the skew angle so that the leading edge is perpendicular to the direction of rotation, or by compensating for the skew angle during rotation of the sheet through a finite angle while repositioning the sheet (e.g. from landscape to portrait mode or vice versa).
According to one aspect of the present invention, a method of reorienting a sheet having a skew using first and second drive means, rotating first and second rollers, respectively, independently of each other, and first and second sensors, is provided. The method comprises the steps of: (a) Feeding the sheet, with a leading edge and in a first orientation, in a first direction to a location adjacent the first and second rollers, at which the rollers engage the sheet. (b) at a location adjacent the first and second rollers, sensing the leading edge of the sheet with the sensors. (c) If the leading edge reaches one sensor before it reaches the other sensor, determining the distance of movement of the sheet in the first direction between sensor activations. (d) Utilizing the distance determined from step (c), calculating the angle of skew of the leading edge of the sheet; and (e) in response to (d), controlling the drive means to, in turn, control the speed and direction of rotation of the rollers, so that the rollers rotate the sheet to compensate for the skew angle to dispose the sheet in a desired second orientation. Step (d) is preferably practiced by calculating the tangent of the skew angle.
In the method according to the present invention, there may be the further step (f), in conjunction with step (e), of controlling the drive means to, in turn, control the speed and direction of the rollers, so that the rollers rotate the sheet through a predetermined angle even if the sheet is not originally skewed, so that it has the second orientation whether or not the sheet is originally skewed. There may also be the further step (g) after steps (e) and (f), of conveying a sheet in the first direction. Step (b) is preferably practiced at a location less than one-half of the dimension of the sheet in the first direction when it has the first orientation, and under the sheet while step (e) is practiced.
According to another aspect of the present invention, a sheet handling assembly is provided. The sheet handling assembly comprises: A substantially planar, generally horizontal, conveyance surface. First and second driven shafts having substantially in-line axes of rotation. First and second rollers driven by the first and second driven shafts, respectively, independently of each other, and spaced from each other along the axes of rotation. The first and second rollers each having a circumferential peripheral surface portion thereof extending up through the generally horizontal surface, so that the peripheral surface of each is above the generally horizontal surface. First and second sensors each having a sensing element extending into a position along the generally horizontal surface adjacent the rollers, the sensors spaced from each other in a direction parallel to the in-line axes of rotation of the rollers; and a controller operatively connected to the driven shafts and to said first and second sensors. The rollers are spaced from each other in a direction parallel to the in-line axes of rotation a distance equal to the spacing between the rollers along the axes of rotation. The first sensor is in alignment with the first roller, and the second sensor is in alignment with the second roller in a dimension perpendicular to the in-line axes of rotation of the rollers. The sensors may comprise photosensors, and conveyor means may be provided cooperating with the horizontal surface for conveying a sheet into operative association with, and away from the rollers and sensors.
According to yet another aspect of the present invention, apparatus for rotating the sheet is provided comprising: A conveyance surface on which a sheet, having a first orientation, travels in a first direction. First and second rollers for engaging a sheet travelling on the conveyance surface and spaced from each other in a second direction, generally transverse to the first direction. First and second drive means, operatively driving the first and second rollers, respectively, independently of each other. Sensing means for sensing the leading edge of a sheet, having the first orientation, with respect to the rollers. Control means for controlling the speed and direction of rotation of the drive means in response to the sensing means to rotate the sheet so that it has a predetermined second orientation, significantly angularly displaced from the first orientation; and wherein the sensing means further comprises means for sensing if the leading edge of a sheet is skewed with respect to the second direction, and wherein the control means comprise means, in response to a determination that the leading edge is skewed, of controlling the speed and direction of rotation of the drive means to compensate for the skew orientation of the sheet leading edge so that it is displaced to the desired predetermined second orientation, with the skew automatically compensated for. The drive means are preferably reversible motors, such as D.C. stepper motors. The sensing means comprise first and second sensors spaced from each other a predetermined distance in the second direction in a line on a center line perpendicular to the first direction, and are preferably spaced apart the same distance as the rollers in center lines parallel to them, and downstream from them.
It is the primary object of the present invention to provide a method and apparatus for compensating for the skew angle of sheets during the feeding thereof, including during rotation of the sheets from one orientation to another. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.